1. Field of the Invention
This invention relates generally to slide fasteners or zippers and more particularly to a slide fastener stringer having coupling elements secured to a coated support tape.
2. Prior Art
Various slide fastener stringers are known comprising a base woven or knitted tape which is coated on both sides with a cover layer such as of rubber, elastomeric materials and the like.
A typical relevant prior art is disclosed in Japanese Utility Model Laid-Open Publication No. 62-171912 in which a stringer tape is coated with an elastomeric material such as vinyl chloride and has a row of coupling elements sewn onto one of its longitudinal edge portions which are substantially as thick as the remaining web portion of the tape. The coupling elements may thus be firmly secured in place on the tape by virtue of the repulsive or bounce-back action of the elastomeric coats on compression by the sewing pressure. However, the coated layers are susceptible to debilitation of their repulsive force in use over extended periods of time, resulting in reduced tension of the sewn seams and hence loosened coupling elements, leading to malfunction of the slide fastener. This problem is pronounced in the case where a slide fastener having such coated stringer tapes is subjected to severe lateral pull as when applied to a fully packed bag or the like.